JP2006274083A - Ink composition, ink jet recording method, printed article, method for producing lithographic printing plate and lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition which is highly sensitively cured by the irradiation of radiations, can form images having high image qualities and excellent adhesiveness to recording media, and has good storage stability, to provide an ink jet recording method using the ink composition, to provide a printed article obtained by the ink jet recording method, to provide a lithographic printing plate having high printing resistance and obtained from the ink composition, and to provide a method for producing the lithographic printing plate. <P>SOLUTION: This ink composition is characterized by comprising (a) a polymer having mercapto group-bound heterocyclic groups, (b) a polymerizable compound, and (c) a polymerization initiator. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink composition suitably used for ink jet recording, an ink jet recording method, and a printed material using the ink composition, a lithographic printing plate obtained using the ink, and a method for producing a lithographic printing plate. is there. More specifically, an ink composition that can be cured with high sensitivity to radiation irradiation, can form a high-quality image, and has good storage stability, an ink-jet recording method, And a printed matter using the same, a lithographic printing plate obtained using the ink, and a method for producing the lithographic printing plate.

  As an image recording method for forming an image on a support such as paper based on an image data signal, there are an electrophotographic method, a sublimation type and a melt type thermal transfer method, an ink jet method and the like. In particular, the ink jet method can be implemented with an inexpensive apparatus, and ink is ejected only to the required image area on the support to form an image directly, so that the ink can be used efficiently and the running cost is reduced. Is cheap. Furthermore, it is excellent in that the apparatus is simple and noise is low.

As one of such ink jet type image recording methods, there is a method of fixing ink on a support using an ink that is cured by irradiation with radiation such as ultraviolet rays. Ink-jet recording inks that can be cured by irradiation with radiation such as ultraviolet rays, which are used in this method, have a relatively low odor, are quick-drying, have no ink absorbability, and are usually difficult to directly record. (For example, it is known that there is a feature that an image having no blur, high sensitivity, and high adhesion can be obtained with respect to (for example, a plastic sheet or a metal plate) (for example, Patent Documents 1 to 5). reference.).
In addition to the above characteristics, for the purpose of providing an ink for inkjet recording that has low irritation and sensitization even when applied to the skin and has high safety, a polymerizable compound and a color composed of a specific radical polymerization type acrylate compound group are provided. A composition containing a material has been proposed (see, for example, Patent Documents 6 and 7).

  When such a radiation curable ink for ink jet recording is employed, high sensitivity to radiation and high image quality of an image formed by a fixed ink are required. If the sensitivity to radiation is sufficiently high, there are many benefits such as high curability, reduction of power consumption of the radiation source, longer life by reducing the load on the radiation source, prevention of low molecular weight substances caused by insufficient curing, etc. This is because. In addition, by achieving high sensitivity, particularly when an image portion of a lithographic printing plate for offset printing is formed using ink jet recording ink, the curing strength of the image portion is increased, and high printing durability is achieved. A lithographic printing plate of sex will be obtained.

In general, the use of various polymerization initiation systems has been disclosed as a method for increasing the sensitivity to radiation in a radiation curable polymerizable compound (see, for example, Non-Patent Document 1). However, there is no example in which a polymerization initiating system that satisfies sufficient sensitivity and storage stability for scanning exposure is employed in ink for inkjet recording. Also, there is no known use of a radiation curable ink for ink jet recording that satisfies high printing durability (high adhesion) and high-quality image formation and storage stability for a lithographic printing plate.
JP-A-63-235382 JP-A-3-216379 Japanese Patent Laid-Open No. 5-214280 Japanese Patent Publication No.6-212256 Japanese Patent Publication No. 6-62905 JP 2003-192943 A JP 2003-192944 A Bruce M. Monroe et al., Chemical Review, 93, (1993), pp. 435-448.

An object of the present invention is to solve the conventional problems and achieve the following objects.
That is, an object of the present invention is an ink composition that can be cured with high sensitivity to radiation irradiation, can form a high-quality image with excellent adhesion to a recording medium, and has good storage stability. Another object of the present invention is to provide an ink jet recording method using the ink composition, and a printed matter obtained by the ink jet recording method.
Another object of the present invention is to provide a high printing durability lithographic printing plate obtained by using the ink composition and a method for producing the same.

As a result of intensive studies, the present inventors have found that the above object can be achieved by using an additive having a specific structure, and completed the present invention.
That is, the present invention is as follows.
<1> An ink composition comprising (a) a polymer having a heterocyclic group bonded to a mercapto group in its side chain, (b) a polymerizable compound, and (c) a polymerization initiator. .
<2> (d) The ink composition according to <1>, further comprising a colorant.
<3> The ink composition according to <2>, wherein the colorant (d) is a pigment or an oil-soluble dye.
<4> The ink composition according to <3>, wherein an oxidation potential of the oil-soluble dye is 1.0 V (vs SCE) or more.
<5> The ink composition according to any one of <1> to <4>, which is for inkjet recording.

<6> A step of discharging the ink composition according to any one of <1> to <5> onto a recording medium using an ink jet printer, and curing the ink composition discharged by irradiating with active radiation. An ink jet recording method comprising a step.
<7> The actinic radiation is emitted from a light emitting diode that generates ultraviolet rays having an emission wavelength peak of 360 to 420 nm and a maximum illuminance of 10 to 1,000 mW / cm ^{2 on the} surface of the recording medium. <6> The ink jet recording method according to <6>.
<8> A printed matter obtained by discharging the ink composition according to any one of <1> to <5> onto a recording medium using an ink jet printer, and then irradiating with active radiation to cure the ink composition. .

<9> After discharging the ink composition according to any one of <1> to <5> onto a hydrophilic support, the hydrophobic composition is formed by irradiating the ink composition to cure the ink composition. A method for producing a lithographic printing plate, comprising forming the lithographic printing plate.
<10> Hydrophobic formed by discharging the ink composition according to any one of <1> to <5> onto a hydrophilic support and then irradiating the ink composition to cure the ink composition. A lithographic printing plate having a sex region.

The ink composition of the present invention can be used for normal printing to form an image with high image quality and excellent strength, and not only a high-quality printed matter can be obtained, but also suitable for the production of resists, color filters, and optical discs. It can be used and is also useful as an optical modeling material.
Further, by applying the ink jet recording method, it is possible to directly form an image area with high sensitivity and high intensity on a non-absorbable recording medium based on digital data. The composition is also suitably used for preparing a lithographic printing plate, particularly a lithographic printing plate having a large area of A2 or larger, and the obtained lithographic printing plate has excellent printing durability.

According to the present invention, an ink composition that can be cured with high sensitivity to radiation irradiation, can form a high-quality image with excellent adhesion to a recording medium, and has good storage stability, An ink jet recording method using the ink composition, and a printed matter obtained by the ink jet recording method can be provided.
Further, according to the present invention, by using the ink composition of the present invention, a lithographic printing plate having a high-strength and high-quality image area based on digital data and excellent in printing durability, and a method for producing the same are provided. can do.

The ink composition of the present invention comprises (a) a polymer having a heterocyclic group bonded with a mercapto group in its side chain (hereinafter, referred to as “specific mercapto group-containing polymer” as appropriate), and (b) a polymerizable compound. And (c) a polymerization initiator.
Here, the ink composition of the present invention is cured by applying energy capable of generating active species from (c) a polymerization initiator. This energy is preferably actinic radiation, and the actinic radiation widely includes α rays, γ rays, X rays, ultraviolet rays, visible rays, infrared rays, electron rays, etc. From the viewpoint of curing sensitivity and device availability, ultraviolet rays and electron beams are preferable, and ultraviolet rays are particularly preferable. Therefore, the ink composition of the present invention is preferably an ink composition that can be cured by irradiating ultraviolet rays as active radiation.
Hereinafter, each component used in the ink composition of the present invention will be described in order.

[(A) Specific Mercapto Group-Containing Polymer]
The (a) specific mercapto group-containing polymer constituting the ink composition of the present invention may have a heterocyclic group to which a mercapto group is directly bonded in the side chain. It may be bonded to a cyclic group.
By using this specific mercapto group-containing polymer, in the radical polymerization system, hydrogen is donated to the radical generated during the polymerization, so that the chain mobility can be promoted and the polymerization efficiency can be improved. In addition, when polymerization is initiated from a mercapto group in a specific mercapto group-containing polymer, the molecular weight change is large and the curability is extremely high because the original structure is a polymer.
Furthermore, by using a specific mercapto group-containing polymer, even in a cationic polymerization system, for example, it functions as a hydrogen donor when an onium salt-type polymerization initiator is photolyzed, improving the amount of acid generation, and increasing the polymerization rate. Can be improved.
In addition, since the specific mercapto group-containing polymer has low mobility compared to the addition of a low-molecular mercapto compound, the stability in the ink composition can also be improved.

The specific mercapto group-containing polymer preferably includes a repeating unit represented by the following general formula (1), general formula (2), or general formula (3).

In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, and X ¹ represents a nitrogen-containing heterocyclic group. L ¹ represents an arbitrary linking group for linking X ¹ and the polymer main chain, and n represents 1 or 2.
In the above general formula (2), X ² represents a nitrogen-containing heterocyclic group. L ² represents an arbitrary linking group for linking X ² and the polymer main chain, and m represents 1 or 2.
In the above general formula (3), X ³ represents a nitrogen-containing heterocyclic group. L ³ represents an arbitrary linking group for linking X ³ and the polymer main chain, and p represents 1 or 2.

Examples of the nitrogen-containing heterocyclic group represented by X ¹ , X ² or X ³ include a pyrrole ring, pyrazole ring, imidazole ring, triazole ring, tetrazole ring, isoxazole ring, oxazole ring, oxadiazole ring, Thiazole ring, thiazole ring, thiadiazole ring, thiatriazole ring, indole ring, indazole ring, benzimidazole ring, benzotriazole ring, benzoxazole ring, benzthiazole ring, benzselenazole ring, benzothiadiazole ring, pyridine ring, pyridazine ring, Examples include a pyrimidine ring, a pyrazine ring, a triazine ring, a quinoline ring, a quinoxaline ring, and the like, and a substituent other than a mercapto group may be bonded thereto.

As the linking group represented by L ¹ , L ² , or L ³ , any group can be used, but an alkylene group, an arylene group, an aralkylene group, a COO group, an NHCOO group, and an NHCOOC ₂ H ₄ group. , A CONH group, a group represented by the following general formula (4), or a divalent linking group such as a combination of these is preferred.

In General Formula (4), R ² represents a hydrogen atom or an alkoxy group. Examples of the alkoxy group include a methoxy group, an ethoxy group, a butoxy group, and a hexyl group.

  Specific examples (m-1) to (m-12) of monomers for obtaining a repeating unit represented by the following general formula (1), general formula (2), or general formula (3) are shown below. The present invention is not limited to this.

The specific mercapto group-containing polymer in the present invention is obtained by polymerizing a monomer having a heterocyclic group to which a mercapto group is directly bonded, including specific examples (m-1) to (m-12) of the monomer as described above. be able to.
If the monomer having a mercapto group is polymerized as it is, a chain transfer reaction may occur due to attack of a polymerization radical on the mercapto group, and a desired polymer may not be obtained. Therefore, the synthesis method of the specific mercapto group-containing polymer in the present invention includes, for example, (1) a method in which a monomer having a heterocyclic group to which a mercapto group is directly bonded is polymerized in a strong alkali, and (2) a mercapto group is directly bonded. A method in which a mercapto group of a monomer having a heterocyclic group is protected with an appropriate protecting group, and then deprotecting, and (3) a nitrogen-containing ring compound directly bonded with a mercapto group and a precursor polymer Using a polymer reaction between the two. Etc. are preferably applied.
In the case of using the method (2), as a method for protecting the mercapto group, for example, a method for converting a mercapto group into a thiolate form by adding various bases such as sodium hydroxide, potassium hydroxide, sodium carbonate, Alternatively, there is a method of converting into a thioester group form such as acetylation. Then, although deprotected after completion of the polymerization, the mercapto group is regenerated by simply neutralizing the thiolate, and in the case of the thioester group, the mercapto group is regenerated by hydrolysis.
Moreover, when using the method of said (3), a reactive group is introduce | transduced into a precursor polymer, and a nitrogen-containing heterocyclic group contains another reactive group couple | bonded with a precursor polymer by reacting with this. It is necessary. These reactive group combinations include hydroxyl group and aldehyde group (acetalization), amino group and aldehyde group (Schiff base formation), amino group and carboxyl group (amide bond formation), hydroxyl group and carboxyl group (esterification), carboxyl Nitrogen-containing heterocyclic groups can be bonded to the precursor polymer by various bonding methods such as a group and a glycidyl group (addition).
In addition, as a method for synthesizing a specific mercapto group-containing polymer in the present invention, the methods described in JP-A Nos. 8-184967, 8-184969, and 8-21614, and the methods shown in the synthesis examples described later are also used. be able to.

In addition, the specific mercapto group-containing polymer in the present invention includes other functional units in addition to the repeating unit having a heterocyclic group directly bonded to a mercapto group as in the general formulas (1) to (3) in the side chain. It may contain a repeating unit having a group in the side chain.
A repeating unit having another functional group in the side chain may be used as a copolymerization component in the polymerization of a monomer having a heterocyclic group to which a mercapto group (including a protected group) is directly bonded. In the polymerization of the precursor polymer, it may be used as a copolymerization component.
As such a monomer for obtaining a repeating unit having another functional group in the side chain, styrene, 4-methylstyrene, 4-hydroxystyrene, 4-acetoxystyrene, 4-carboxystyrene, 4-aminostyrene, Styrene derivatives such as chloromethylstyrene and 4-methoxystyrene; alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, dodecyl methacrylate; Methacrylic acid aryl esters or alkyl aryl esters such as phenyl methacrylate and benzyl methacrylate; 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methoxyethylene methacrylate Methacrylic acid esters having an alkyleneoxy group such as glycol monoester, methoxypolyethylene glycol monoester methacrylate, and polypropylene glycol monoester methacrylate; amino group-containing methacrylic groups such as 2-dimethylaminoethyl methacrylate and 2-diethylaminoethyl methacrylate Acid esters; examples similar to these corresponding methacrylic esters as acrylic esters; carboxy groups such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, maleic acid monoalkyl ester, fumaric acid monoalkyl ester Amino-containing monomers such as allylamine and diallylamine; vinyl sulfonic acid and its salt, allyl sulfonic acid and its salt, methallyl sulfonic acid and its , Monomers having a sulfonic acid group such as styrenesulfonic acid and its salt, 2-acrylamido-2-methylpropanesulfonic acid and its salt; 4-vinylpyridine, 2-vinylpyridine, N-vinylimidazole, N-vinylcarbazole Monomers having a nitrogen-containing heterocyclic ring such as 4-vinylbenzyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, quaternized product of dimethylaminopropylacrylamide with methyl chloride, N-vinylimidazole Monomers having a quaternary ammonium base such as quaternized products with methyl chloride and 4-vinylbenzylpyridinium chloride; acrylamide, methacrylamide, dimethyl Acrylamide or methacrylamide derivatives such as ruacrylamide, diethylacrylamide, N-isopropylacrylamide, diacetoneacrylamide, N-methylolacrylamide, N-methoxyethylacrylamide, 4-hydroxyphenylacrylamide; vinyl acetate, vinyl chloroacetate, vinyl propionate, Vinyl esters such as vinyl butyrate, vinyl stearate and vinyl benzoate; vinyl ethers such as methyl vinyl ether and butyl vinyl ether; others, acrylonitrile, methacrylonitrile, phenylmaleimide, hydroxyphenylmaleimide, N-vinylpyrrolidone, acryloylmorpholine, tetrahydro Furfuryl methacrylate, vinyl chloride, vinylidene chloride, allyl alcohol, vinyl Silane, glycidyl methacrylate and various monomers.

In addition, the specific mercapto group-containing polymer in the present invention preferably has solubility in a monomer (polymerizable compound) in the ink composition, and specifically includes a carboxyl group and a phenolic hydroxyl group in the polymer. It preferably has a solubility-improving substituent such as an ethyleneoxy group. This solubility-improving substituent may be directly bonded to the main chain of the specific mercapto group-containing polymer, or may be bonded to a side chain.
In order to introduce such a kalkari-soluble group into a specific mercapto group-containing polymer, among other monomers listed above, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, maleic acid monoalkyl ester, Monomers having a carboxy group such as fumaric acid monoalkyl ester and 4-carboxystyrene may be used.
Moreover, it is preferable that the ratio of the monomer which has these solubility improvement substituents in a specific mercapto group containing polymer contains 99 mol% or less, More preferably, it is a ratio of 90 mol% or less.

  Hereinafter, although the specific example of the specific mercapto group containing polymer in this invention is shown, this invention is not limited to this. In addition, in each repeating unit shown below, a number represents molar ratio.

  The molecular weight of such a specific mercapto group-containing polymer is preferably in the range of 1,000 to 1,000,000 and more preferably in the range of 10,000 to 200,000 in terms of weight average molecular weight.

  In addition, the ratio of the repeating unit having a heterocyclic group directly bonded to a mercapto group contained in the specific mercapto group-containing polymer is preferably at least 1 mol% or more from the viewpoint of curability, and is preferably 10 mol% or more. More preferably, in order to increase the solubility in the monomer (polymerizable compound) in the ink composition, it is preferably 90 mol% or less.

  Furthermore, the content of the specific mercapto group-containing polymer in the present invention is 1 to 50 mass with respect to the total solid content of the ink composition from the viewpoint of the balance between the growth of the polymerization reaction of the polymerizable compound and the chain mobility. % Range is preferable, the range of 3-40 mass% is more preferable, and the range of 5-30 mass% is still more preferable.

[(B) Polymerizable compound]
The (b) polymerizable compound used in the present invention is not particularly limited as long as it is a compound that causes a polymerization reaction by an active species generated from (c) a polymerization initiator described later and cures. (B-1) Radical A polymerizable compound or (b-2) a cationic polymerizable compound is used.
Hereinafter, the (b-1) radical polymerizable compound and the (b-2) cationic polymerizable compound will be described.

(B-1) Radical polymerizable compound (b-1) The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization, and has at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. And any compound having a chemical form such as a monomer, oligomer, or polymer. Only one kind of such radically polymerizable compounds may be used, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve desired properties. A polyfunctional compound having two or more functional groups is more preferable than a monofunctional compound. More preferably, two or more polyfunctional compounds are used in combination for controlling performance such as reactivity and physical properties.

  Examples of radical polymerizable compounds include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and their salts, esters, urethanes, amides and anhydrides, acrylonitrile, styrene, Furthermore, radically polymerizable compounds such as various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides and unsaturated urethanes can be mentioned. Specifically, 2-ethylhexyl acrylate, stearyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, bis (4-acryloxypolyethoxyphenyl) propane, Neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, pentaerythritol triacrylate , Pentaerythritol tetraa Relate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate, N-methylolacrylamide, diacetone acrylamide, epoxy acrylate, urethane acrylate and other acrylic acid derivatives, methyl methacrylate, n-butyl Methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene Glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, methacryl derivatives such as 2,2-bis (4-methacryloxypolyethoxyphenyl) propane, allyl glycidyl ether, diallyl phthalate, triallyl trimelli Derivatives of allyl compounds such as tate, etc., more specifically, Shinzo Yamashita, “Crosslinker Handbook”, (1981 Taiseisha); Sato Kato, “UV / EB Curing Handbook (raw material)” (1985, Polymer Publications); Radtech Study Group, "Application and Market of UV / EB Curing Technology", 79 pages (1989, CMC); Eiichiro Takiyama, "Polyester Resin Handbook", (1988) Commercial products or industry as described in Nikkan Kogyo Shimbun) And known radically polymerizable or crosslinkable monomers, oligomers and polymers can be used.

(B-2) Cationic polymerizable compound (b-2) As the cationic polymerizable compound, various known cationic polymerizable monomers known as photocation polymerizable monomers can be used. Examples of the cationic polymerizable monomer include various publications such as JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, and JP-A-2001-220526. And epoxy compounds, vinyl ether compounds, oxetane compounds and the like described in the above.

Examples of the epoxy compound include aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.
Aromatic epoxides include di- or polyglycidyl ethers produced by the reaction of polyphenols having at least one aromatic nucleus or their alkylene oxide adducts and epichlorohydrin, such as bisphenol A or its alkylene oxides. Examples thereof include di- or polyglycidyl ethers of adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or its alkylene oxide adducts, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

As the alicyclic epoxide, cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Or a cyclopentene oxide containing compound is mentioned preferably.
Examples of the aliphatic epoxide include dihydric polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. Typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol, or 1,6. -Diglycidyl ether of alkylene glycol such as diglycidyl ether of hexanediol, diglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, diglycidyl of polyethylene glycol or its alkylene oxide adduct Diglycidyl ethers of polyalkylene glycols typified by diglycidyl ethers of ethers, polypropylene glycols or alkylene oxide adducts thereof And the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxy compounds, aromatic epoxides and alicyclic epoxides are preferable from the viewpoint of excellent curing speed, and alicyclic epoxides are particularly preferable.

Examples of the vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, Di- or trivinyl ether compounds such as methylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n-propyl Pills vinyl ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.
As the vinyl ether compound, a di- or trivinyl ether compound is preferable from the viewpoints of curability, adhesion to a recording medium, surface hardness of the formed image, and the like, and a divinyl ether compound is particularly preferable.

The oxetane compound in the present invention refers to a compound having an oxetane ring, and a known oxetane compound can be arbitrarily selected and used as described in JP-A Nos. 2001-220526, 2001-310937, and 2003-341217. .
The compound having an oxetane ring that can be used in the ink composition of the present invention is preferably a compound having 1 to 4 oxetane rings in the structure. By using such a compound, it becomes easy to maintain the viscosity of the ink composition in a good handling property range, and it is possible to obtain high adhesion of the cured ink to the recording medium. .

  Examples of the compound having 1 to 2 oxetane rings in the molecule include compounds represented by the following general formulas (i) to (iii).

In the general formulas (i) to (iii), R ^a1 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, a furyl group, or a thienyl group. Represents. In addition, when two ^Ra1 exists in a molecule ^| numerator, they may be the same or different.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Further, preferred examples of the fluoroalkyl group include those in which any hydrogen of these alkyl groups is substituted with a fluorine atom.

In the general formula (i), R ^a2 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a group having an aromatic ring, or an alkylcarbonyl having 2 to 6 carbon atoms. Group, an alkoxycarbonyl group having 2 to 6 carbon atoms, and an N-alkylcarbamoyl group having 2 to 6 carbon atoms.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkenyl group include a 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenyl group, and 2-methyl-2. -Propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group and the like. Examples of the group having an aromatic ring include phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group, phenoxyethyl group and the like. Can be mentioned.
Examples of the alkylcarbonyl group include an ethylcarbonyl group, a propylcarbonyl group, and a butylcarbonyl group. Examples of the alkoxycarbonyl group include an ethoxycarbonyl group, a propoxycarbonyl group, and a butoxycarbonyl group. As the N-alkylcarbamoyl group, Includes an ethylcarbamoyl group, a propylcarbamoyl group, a butylcarbamoyl group, a pentylcarbamoyl group, and the like.

In the general formula (ii), R ^a3 represents a linear or branched alkylene group, a linear or branched poly (alkyleneoxy) group, a linear or branched unsaturated hydrocarbon group, a carbonyl group or a carbonyl group. An alkylene group containing a group, an alkylene group containing a carboxyl group, an alkylene group containing a carbamoyl group, or a group shown below is represented.
Examples of the alkylene group include an ethylene group, a propylene group, and a butylene group. Examples of the poly (alkyleneoxy) group include a poly (ethyleneoxy) group and a poly (propyleneoxy) group.
Examples of the unsaturated hydrocarbon group include a propenylene group, a methylpropenylene group, and a butenylene group.

In the polyvalent group, R ^a4 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a nitro group, a cyano group, a mercapto group, a lower alkyl carboxyl group, Represents a carboxyl group or a carbamoyl group.
R ^a5 represents an oxygen atom, a sulfur atom, a methylene group, NH, SO, SO ₂ , C (CF ₃ ) ₂ , or C (CH ₃ ) ₂ .
R ^a6 represents an alkyl group having 1 to 4 carbon atoms or an aryl group, and n is an integer of 0 to 2000.
R ^a7 represents an alkyl group having 1 to 4 carbon atoms, an aryl group, or a monovalent group having the following structure.

In the monovalent group, R ^a8 is an alkyl group having 1 to 4 carbon atoms or an aryl group, and m is an integer of 0 to 100.

  Examples of the compound having 3 to 4 oxetane rings include compounds represented by the following general formula (iv).

In formula (iv), R ^a1 has the same meaning as R ^a1 in Formula (i). R ^a9 is a polyvalent linking group, for example, a branched alkylene group having 1 to 12 carbon atoms such as groups represented by A to C below, and a branched poly group such as a group represented by D below. Examples include (alkyleneoxy) groups or branched polysiloxy groups such as groups represented by E below. j is 3 or 4.

In the above A, R ^a10 represents a methyl group, an ethyl group, or a propyl group. Moreover, in said D, p is an integer of 1-10.

  Another embodiment of the oxetane compound that can be suitably used in the present invention includes a compound represented by the following general formula (v) having an oxetane ring in the side chain.

In formula (v), R ^a1 has the same meaning as R ^a1 in Formula (i). R ^a8 has the same meaning as R ^a8 in the general formula (iv). R ^a11 is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, or a trialkylsilyl group, and r is 1 to 4.

The compound having such an oxetane ring is described in detail in the above-mentioned JP-A No. 2003-341217, paragraphs [0048] to [0084], and the compounds described therein can be suitably used in the present invention.
Among the oxetane compounds used in the present invention, it is preferable to use a compound having one oxetane ring from the viewpoint of the viscosity and tackiness of the ink composition.

In the ink composition of the present invention, these polymerizable compounds may be used alone or in combination of two or more, but from the viewpoint of effectively suppressing shrinkage during ink curing. It is preferable to use at least one oxetane compound and at least one compound selected from an epoxy compound and a vinyl ether compound in combination.
The content of the polymerizable compound (b) in the ink composition of the present invention is 98 to 50% by mass based on the total solid content of the ink composition from the viewpoint of sensitivity based on polymerization reactivity and the viscosity of the ink composition. Preferably, it is 95-60 mass%, More preferably, it is the range of 90-70 mass%.

[(C) Polymerization initiator]
The ink composition of the present invention requires (c) a polymerization initiator. Examples of the polymerization initiator include known radical polymerization or cationic polymerization photopolymerization initiator used in radiation-curable ink compositions. The photopolymerization initiator used in the present invention undergoes a chemical change through the action of light or the interaction with the electronically excited state of the sensitizing dye, and at least one of radicals, acids and bases is produced. It is a compound to be formed. Specific photopolymerization initiators known among those skilled in the art can be used without limitation. Specifically, for example, Bruce M. et al. Monroe et al., Chemical Review, 93, 435 (1993). R. S. By Davidson, Journal of Photochemistry and biology A: Chemistry, 73.81 (1993). J. P. Faussier “Photoinitiated Polymerization—Theory and Applications”: Rapra Review vol. 9, Report, Rapra Technology (1998). M. Tsunooka et al. , Prog. Polym. Sci. , 21, 1 (1996). Many are described. In addition, a large number of chemical amplification type photoresists and compounds used for photocationic polymerization are described in “Organic Materials for Imaging” edited by Organic Electronics Materials Study Group, Bunshin Publishing (1993), pages 187 to 192). Yes. Further, F.I. D. Saeva, Topics in Current Chemistry, 156, 59 (1990). G. G. Maslak, Topics in Current Chemistry, 168, 1 (1993). H., et al. B. Shuster et al, JACS, 112, 6329 (1990). , I. D. F. Eaton et al, JACS, 102, 3298 (1980). A group of compounds that undergo oxidative or reductive bond cleavage through interaction with the electronically excited state of the sensitizing dye as described in the above.

  Preferred photopolymerization initiators include (A) aromatic ketones, (B) aromatic onium salt compounds, (C) organic peroxides, (D) hexaarylbiimidazole compounds, (E) ketoxime ester compounds, (F) borate compounds, (G) azinium compounds, (H) metallocene compounds, (I) active ester compounds, (J) compounds having a carbon halogen bond, and the like.

  (A) As a preferable example of aromatic ketones, “RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY” P. FOUASSIER J.M. F. Examples include compounds having a benzophenone skeleton or a thioxanthone skeleton described in RABEK (1993), p77-117. More preferable examples of (A) aromatic ketones include α-thiobenzophenone compounds described in JP-B-47-6416, benzoin ether compounds described in JP-B-47-3981, and JP-B-47-22326. Α-substituted benzoin compounds, benzoin derivatives described in JP-B-47-23664, aroylphosphonic acid esters described in JP-A-57-30704, dialkoxybenzophenones described in JP-B-60-26483, Benzoin ethers described in JP-A-60-26403, JP-A-62-181345, JP-B-1-34242, US Pat. No. 4,318,791, and α-aminobenzophenones described in European Patent 0284561A1, P-di (dimethyla) described in JP-A-2-211452 Nobenzoyl) benzene, thio-substituted aromatic ketone described in JP-A-61-194062, acylphosphine sulfide described in JP-B-2-9597, acylphosphine described in JP-B-2-9596, JP-B-63- Examples thereof include thioxanthones described in Japanese Patent No. 61950, and coumarins described in Japanese Patent Publication No. 59-42864.

  (B) As aromatic onium salt compounds, elements of Group V, VI and VII of the Periodic Table, specifically N, P, As, Sb, Bi, O, S, Se, Te, or I Aromatic onium salts are included. For example, iodonium salts described in European Patent No. 104143, US Pat. No. 4,837,124, Japanese Patent Laid-Open No. 2-150848, Japanese Patent Laid-Open No. 2-96514, European Patent Nos. 370693, 233567, and 297443 are disclosed. The diazonium salts described in the specifications of U.S. Pat. Nos. 2,974,242,279,210 and 422570, U.S. Pat. Benzenediazonium which may have a substituent), diazonium salt resins (formaldehyde resin of diazodiphenylamine, etc.), N-alkoxypyridinium salts, etc. (for example, US Pat. No. 4,743,528, JP-A-63) -138345, JP-A-63 142345, JP-A-63-142346, and JP-B-46-42363, specifically 1-methoxy-4-phenylpyridinium tetrafluoroborate, etc.) The compounds described in JP-A 52-147277, 52-14278, and 52-14279 are preferably used. Generates radicals and acids as active species.

  (C) The organic peroxide includes almost all organic compounds having one or more oxygen-oxygen bonds in the molecule. Examples thereof include 3,3′4,4′-tetra- (t -Butylperoxycarbonyl) benzophenone, 3,3'4,4'-tetra- (t-amylperoxycarbonyl) benzophenone, 3,3'4,4'-tetra- (t-hexylperoxycarbonyl) benzophenone, 3,3′4,4′-tetra- (t-octylperoxycarbonyl) benzophenone, 3,3′4,4′-tetra- (cumylperoxycarbonyl) benzophenone, 3,3′4,4′-tetra Peroxide esters such as-(p-isopropylcumylperoxycarbonyl) benzophenone and di-t-butyldiperoxyisophthalate are preferred.

  (D) Examples of hexaarylbiimidazole compounds include lophine dimers described in JP-B Nos. 45-37377 and 44-86516, such as 2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-bromophenyl) -4,4 ′, 5,5′tetraphenylbiimidazole, 2,2′-bis (o, p-dichlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-chlorophenyl) -4,4', 5,5'-tetra (m-methoxyphenyl) biimidazole, 2, 2′-bis (o, o′-dichlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-nitrophenyl) -4,4 ′, 5,5 ′ − Traphenylbiimidazole, 2,2′-bis (o-methylphenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-trifluorophenyl) -4,4 Examples include ', 5,5'-tetraphenylbiimidazole.

(E) Examples of ketoxime ester compounds include 3-benzoyloxyiminobutan-2-one, 3-acetoxyiminobutan-2-one, 3-propionyloxyiminobutan-2-one, and 2-acetoxyiminopentane-3. -One, 2-acetoxyimino-1-phenylpropan-1-one, 2-benzoyloxyimino-1-phenylpropan-1-one, 3-p-toluenesulfonyloxyiminotan-2-one, 2-ethoxy And carbonyloxyimino-1-phenylpropan-1-one.
Examples of (F) borate compounds include compounds described in the specifications of US Pat. Nos. 3,567,453, 4,343,891, European Patents 109,772 and 109,773. Can be mentioned.

  Examples of (G) azinium salt compounds include JP-A 63-138345, JP-A 63-142345, JP-A 63-142346, JP-A 63-143537, and JP-B 46-42363. The compound group which has NO bond of each gazette description can be mentioned.

  Examples of (H) metallocene compounds include titanocenes described in JP-A-59-152396, JP-A-61-151197, JP-A-63-41484, JP-A-2-249, and JP-A-2-4705. Examples thereof include iron-arene complexes described in JP-A-1-304453 and JP-A-1-152109.

  Specific examples of the titanocene compound include di-cyclopentadienyl-Ti-di-chloride, di-cyclopentadienyl-Ti-bis-phenyl, and di-cyclopentadienyl-Ti-bis-2,3. 4,5,6-pentafluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl, di-cyclopentadienyl-Ti- Bis-2,4,6-trifluorophen-1-yl, di-cyclopentadienyl-Ti-2,6-difluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,4 -Difluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl, di-methylcyclopentadienyl-Ti- -2,3,5,6-tetrafluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,4-difluorophen-1-yl, bis (cyclopentadienyl) -bis (2,6-difluoro-3- (pyridin-1-yl) phenyl) titanium, bis (cyclopentadienyl) bis [2,6-difluoro-3- (methylsulfonamido) phenyl] titanium, bis (cyclopenta And dienyl) bis [2,6-difluoro-3- (N-butylbialoyl-amino) phenyl] titanium.

  Examples of (I) active ester compounds include the specifications of European Patent Nos. 0290750, 046083, 156153, 271851, and 0388343, U.S. Pat. Nos. 3,901,710, and 4,181,531. Nitrobenzol ester compounds described in JP-A-60-198538 and JP-A-53-133022, European Patent Nos. 0199672, 84515, 199672, 0441115, and 0101122. No. 4,618,564, U.S. Pat. No. 4,371,605 and U.S. Pat. No. 4,431,774, JP-A 64-18143, JP-A-2-245756, and JP-A-4-365048. Iminosulfonate compounds, Japanese Examined Patent Publication Nos. 62-6223 and 63 No. 14340, and compounds, and the like described in the JP-A No. 59-174831.

  (J) Preferable examples of the compound having a carbon halogen bond include, for example, Wakabayashi et al., Bull. Chem. Soc. Examples include compounds described in Japan, 42, 2924 (1969), compounds described in British Patent No. 1388492, compounds described in JP-A-53-133428, compounds described in German Patent No. 3333724, and the like. it can.

  F.F. C. J. Schaefer et al. Org. Chem. 29, 1527 (1964), compounds described in JP-A-62-258241, compounds described in JP-A-5-281728, and the like. A compound as described in German Patent No. 2641100, a compound described in German Patent No. 3333450, a group of compounds described in German Patent No. 3021590, or a group of compounds described in German Patent No. 3021599, etc. Can be mentioned.

  Preferable specific examples of the compounds represented by the above (A) to (J) include those shown below.

In the ink composition of the present invention, these polymerization initiators may be used alone or in combination of two or more.
Among the above polymerization initiators, (A) an aromatic ketone, (B) an aromatic onium, from the viewpoint that excellent sensitivity and adhesion after curing can be obtained by combined use with a specific mercapto group-containing polymer. Salt compounds and (D) hexaarylbiimidazole compounds are preferred.

  The content of the polymerization initiator in the ink composition of the present invention is preferably 1 to 30% by mass, and 2 to 25% by mass, based on the total solid content of the ink composition, from the viewpoint of photocurability and time stability. Is more preferable, and still more preferably in the range of 3 to 20 mass%.

  In the ink composition of the present invention, various additives can be used in combination with the essential components according to the purpose. These optional components will be described.

[(D) Colorant]
A visible image can be formed by adding a colorant (d) to the ink composition of the present invention. For example, when forming an image area of a lithographic printing plate, it is not always necessary to add it, but it is also preferable to use a colorant from the viewpoint of plate inspection of the obtained lithographic printing plate.
There is no restriction | limiting in particular in the coloring agent which can be used here, According to a use, well-known various color materials and (pigment, dye) can be selected suitably, and can be used. For example, when forming an image excellent in weather resistance, a pigment is preferable. As the dye, both water-soluble dyes and oil-soluble dyes can be used, but oil-soluble dyes are preferred.

(Pigment)
The pigment is not particularly limited, and all commercially available organic and inorganic pigments or pigments dispersed in an insoluble resin or the like as a dispersion medium, or the resin is grafted onto the pigment surface Can be used. Moreover, what dye | stained the resin particle with dye can be used.
Examples of these pigments include, for example, “Pigment Dictionary” (2000), edited by Seijiro Ito. Herbst, K.M. Hunger “Industrial Organic Pigments”, JP 2002-12607 A, JP 2002-188025 A, JP 2003-26978 A, and JP 2003-342503 A3.

  Specific examples of organic pigments and inorganic pigments that can be used in the present invention include C.I. I. Pigment Yellow 1 (Fast Yellow G etc.), C.I. I. A monoazo pigment such as C.I. Pigment Yellow 74; I. Pigment Yellow 12 (disaji yellow AAA, etc.), C.I. I. Disazo pigments such as C.I. Pigment Yellow 17; I. Non-benzidine type azo pigments such as CI Pigment Yellow 180; I. Azo lake pigments such as C.I. Pigment Yellow 100 (eg Tartrazine Yellow Lake); I. Condensed azo pigments such as CI Pigment Yellow 95 (Condensed Azo Yellow GR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Yellow 115 (such as quinoline yellow lake); I. Basic dye lake pigments such as CI Pigment Yellow 18 (Thioflavin Lake, etc.), anthraquinone pigments such as Flavantron Yellow (Y-24), isoindolinone pigments such as Isoindolinone Yellow 3RLT (Y-110), and quinophthalone yellow Quinophthalone pigments such as (Y-138), isoindoline pigments such as isoindoline yellow (Y-139), C.I. I. Nitroso pigments such as C.I. Pigment Yellow 153 (nickel nitroso yellow, etc.); I. And metal complex salt azomethine pigments such as CI Pigment Yellow 117 (copper azomethine yellow, etc.).

  C. As a thing which exhibits red or magenta color. I. Monoazo pigments such as CI Pigment Red 3 (Toluidine Red, etc.); I. Disazo pigments such as C.I. Pigment Red 38 (Pyrazolone Red B, etc.); I. Pigment Red 53: 1 (Lake Red C, etc.) and C.I. I. Azo lake pigments such as C.I. Pigment Red 57: 1 (Brilliant Carmine 6B); I. Condensed azo pigments such as C.I. Pigment Red 144 (condensed azo red BR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Red 174 (Phloxine B Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Red 81 (Rhodamine 6G 'lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Red 177 (eg, dianthraquinonyl red); I. Thioindigo pigments such as C.I. Pigment Red 88 (Thioindigo Bordeaux, etc.); I. Perinone pigments such as C.I. Pigment Red 194 (perinone red, etc.); I. Perylene pigments such as C.I. Pigment Red 149 (perylene scarlet, etc.); I. Pigment violet 19 (unsubstituted quinacridone), C.I. I. Quinacridone pigments such as CI Pigment Red 122 (quinacridone magenta, etc.); I. Isoindolinone pigments such as CI Pigment Red 180 (isoindolinone red 2BLT, etc.); I. And alizarin lake pigments such as CI Pigment Red 83 (Mada Lake, etc.).

  As a pigment exhibiting blue or cyan, C.I. I. Disazo pigments such as C.I. Pigment Blue 25 (Dianisidine Blue, etc.); I. Phthalocyanine pigments such as C.I. Pigment Blue 15 (phthalocyanine blue, etc.); I. Acidic dye lake pigments such as C.I. Pigment Blue 24 (Peacock Blue Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Blue 1 (Viclotia Pure Blue BO Lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Blue 60 (Indantron Blue, etc.); I. And alkali blue pigments such as CI Pigment Blue 18 (Alkali Blue V-5: 1).

As a pigment exhibiting green, C.I. I. Pigment green 7 (phthalocyanine green), C.I. I. Phthalocyanine pigments such as C.I. Pigment Green 36 (phthalocyanine green); I. And azo metal complex pigments such as CI Pigment Green 8 (Nitroso Green).
As a pigment exhibiting an orange color, C.I. I. An isoindoline pigment such as C.I. Pigment Orange 66 (isoindoline orange); I. And anthraquinone pigments such as CI Pigment Orange 51 (dichloropyrantron orange).

Examples of the black pigment include carbon black, titanium black, and aniline black.
Specific examples of the white pigment include basic lead carbonate (2PbCO ₃ Pb (OH) ₂ , so-called silver white), zinc oxide (ZnO, so-called zinc white), titanium oxide (TiO ₂ , so-called titanium white), Strontium titanate (SrTiO ₃ , so-called titanium strontium white) or the like can be used.

  Here, titanium oxide has a smaller specific gravity than other white pigments, a large refractive index, and is chemically and physically stable, so that it has a large hiding power and coloring power as a pigment. Excellent durability against other environments. Therefore, it is preferable to use titanium oxide as the white pigment. Of course, other white pigments (may be other than the listed white pigments) may be used as necessary.

For dispersion of the pigment, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, a jet mill, a homogenizer, a paint shaker, a kneader, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, or a wet jet mill is used. Can do.
It is also possible to add a dispersant when dispersing the pigment. Examples of the dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a high molecular weight unsaturated acid ester, a high molecular weight copolymer, a modified polyacrylate, an aliphatic polyacrylate. Carboxylic acid, naphthalenesulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester, pigment derivative and the like. It is also preferable to use a commercially available polymer dispersant such as the Solsperse series from Zeneca.
Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment.

  As a dispersion medium for various components such as pigments in the ink composition, a solvent may be added, and the polymerizable compound (b) which is a low molecular weight component without solvent may be used as a dispersion medium. The ink composition of the present invention is a radiation curable ink, and is preferably solvent-free in order to cure the ink after it is applied to a recording medium. This is because if the solvent remains in the cured ink image, the solvent resistance is deteriorated or a VOC (Volatile Organic Compound) problem of the remaining solvent occurs. From such a viewpoint, as the dispersion medium, (b) a polymerizable compound is used, and among them, it is preferable to select a cationically polymerizable monomer having the lowest viscosity from the viewpoint of improving dispersibility and handling properties of the ink composition.

The average particle size of the pigment particles is preferably 0.08 to 0.5 μm, and the maximum particle size is 0.3 to 10 μm, preferably 0.3 to 3 μm. Set selection, dispersion conditions, and filtration conditions. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.
The colorant is preferably added in an amount of 1 to 10% by mass in terms of solid content in the ink composition, and more preferably 2 to 8% by mass.

(dye)
Next, (d) the dye preferably used as the colorant in the present invention will be described.
The dye can be appropriately selected from conventionally known compounds (dyes). Specific examples include dyes described in paragraphs [0023] to [0089] of JP-A No. 2002-114930.

  Examples of yellow dyes include, for example, phenols, naphthols, anilines, pyrazolones, pyridones, aryl or heteryl azo dyes having open-chain active methylene compounds as coupling components, for example, open-chain active methylene compounds as coupling components Azomethine dyes having, for example, methine dyes such as benzylidene dyes and monomethine oxonol dyes, for example, quinone dyes such as naphthoquinone dyes and anthraquinone dyes, and other dyes include quinophthalone dyes, nitro, Nitroso dyes, acridine dyes, acridinone dyes and the like can be mentioned.

  Examples of the magenta dye include phenols, naphthols, anilines, pyrazolones, pyridones, pyrazolotriazoles, and ring-closing active methylene compounds (for example, dimedone, barbituric acid, 4-hydroxycoumarin) as coupling components. Derivatives), electron-rich heterocycles (eg, pyrrole, imidazole, thiophene, thiazole derivatives), or aryl or heteryl azo dyes, eg, azomethine dyes having pyrazolones, pyrazolotriazoles as coupling components, eg, arylidene dyes, styryl Dyes, merocyanine dyes, methine dyes such as oxonol dyes, carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes, such as naphthoquinone, anthraquinone, anthrone Quinone dyes such Rapiridon, it can be mentioned condensed polycyclic dyes such as, for example, dioxazine dye.

  Examples of cyan dyes include azomethine dyes such as indoaniline dyes and indophenol dyes, cyanine dyes, oxonol dyes, polymethine dyes such as merocyanine dyes, diphenylmethane dyes, triphenylmethane dyes, carbonium dyes such as xanthene dyes, Examples of phthalocyanine dyes and anthraquinone dyes include phenols, naphthols, anilines, pyrrolopyrimidin-one, aryl or heteryl azo dyes having pyrrolotriazin-one derivatives, and indigo / thioindigo dyes as coupling components.

  Each of the dyes may exhibit yellow, magenta, and cyan colors only after a part of the chromophore is dissociated. In this case, the counter cation is an inorganic cation such as an alkali metal or ammonium. Alternatively, it may be an organic cation such as pyridinium, quaternary ammonium salt, or a cationic polymer having a partial structure thereof.

  The dye used in the present invention is preferably oil-soluble. Specifically, it means that the solubility in water at 25 ° C. (the mass of the dye dissolved in 100 g of water) is 1 g or less, preferably 0.5 g or less, more preferably 0.1 g or less. Therefore, a so-called water-insoluble oil-soluble dye is preferably used.

The dye used in the present invention preferably has an oil-solubilizing group introduced into the above-described dye mother core in order to dissolve the necessary amount in the ink composition.
As the oil-solubilizing group, long chain, branched alkyl group, long chain, branched alkoxy group, long chain, branched alkylthio group, long chain, branched alkylsulfonyl group, long chain, branched acyloxy group, long chain, branched alkoxycarbonyl group, Long chain, branched acyl group, long chain, branched acylamino group long chain, branched alkylsulfonylamino group, long chain, branched alkylaminosulfonyl group and these long chains, aryl groups containing branched substituents, aryloxy groups, aryloxycarbonyl Group, arylcarbonyloxy group, arylaminocarbonyl group, arylaminosulfonyl group, arylsulfonylamino group and the like.
In addition, for water-soluble dyes having carboxylic acid and sulfonic acid, long chain, branched alcohol, amine, phenol, aniline derivatives are used as oil-solubilizing alkoxycarbonyl groups, aryloxycarbonyl groups, alkylaminosulfonyl groups, A dye may be obtained by conversion to an arylaminosulfonyl group.

The oil-soluble dye preferably has a melting point of 200 ° C. or lower, more preferably has a melting point of 150 ° C. or lower, and still more preferably has a melting point of 100 ° C. or lower. By using an oil-soluble dye having a low melting point, pigment crystal precipitation in the ink composition is suppressed, and the storage stability of the ink composition is improved.
Further, it is desirable that the oxidation potential is noble (high) in order to improve fading, particularly resistance to oxidizing substances such as ozone and curing characteristics. For this reason, as the oil-soluble dye used in the present invention, those having an oxidation potential of 1.0 V (vs SCE) or more are preferably used. The oxidation potential is preferably higher, the oxidation potential is more preferably 1.1 V (vs SCE) or more, and particularly preferably 1.15 V (vs SCE) or more.

As the yellow dye, a compound having a structure represented by the general formula (Y-I) described in JP-A No. 2004-250483 is preferable.
Particularly preferred dyes are dyes represented by the general formulas (Y-II) to (Y-IV) described in paragraph No. [0034] of JP-A No. 2004-250483. Examples thereof include compounds described in paragraph numbers [0060] to [0071] of 2004-250483. The oil-soluble dye of the general formula (Y-I) described in the publication may be used not only for yellow but also for inks of any color such as black ink and red ink.

The magenta dye is preferably a compound having a structure represented by the general formulas (3) and (4) described in JP-A No. 2002-114930. Specific examples include paragraphs of JP-A No. 2002-114930. Examples include the compounds described in [0054] to [0073].
Particularly preferred dyes are azo dyes represented by the general formulas (M-1) to (M-2) described in paragraph numbers [0084] to [0122] of JP-A No. 2002-121414, and specific examples Examples include the compounds described in paragraph numbers [0123] to [0132] of JP-A No. 2002-121414. The oil-soluble dyes represented by the general formulas (3), (4) and (M-1) to (M-2) described in the publication are used not only for magenta but also for any color ink such as black ink and red ink. May be.

Examples of cyan dyes include dyes represented by formulas (I) to (IV) described in JP-A No. 2001-181547, and paragraphs [0063] to [0078] of JP-A No. 2002-121414. The dyes represented by the general formulas (IV-1) to (IV-4) are given as preferable examples, and specific examples include paragraph numbers [0052] to [0066] of JP-A No. 2001-181547, Examples thereof include compounds described in JP-A No. 2002-121414, paragraph numbers [0079] to [0081].
Particularly preferred dyes are phthalocyanine dyes represented by general formulas (CI) and (C-II) described in paragraphs [0133] to [0196] of JP-A No. 2002-121414, A phthalocyanine dye represented by formula (C-II) is preferred. Specific examples thereof include the compounds described in JP-A No. 2002-121414, paragraph numbers [0198] to [0201]. The oil-soluble dyes of the formulas (I) to (IV), (IV-1) to (IV-4), (CI) and (C-II) are not only cyan but also black ink or green ink. The ink may be used for any color ink.

-Oxidation potential-
The oxidation potential value (Eox) of the dye in the present invention can be easily measured by those skilled in the art. Regarding this method, for example Delahay, “New Instrumental Methods in Electrochemistry” (1954, published by Interscience Publishers); J. et al. "Electrochemical Methods" by Bard et al. (1980, published by John Wiley & Sons) and Akira Fujishima et al., "Electrochemical Measurement Methods" (published by Gihodo Publishing Co., Ltd., 1984).

Specifically, the oxidation potential is 1 × 10 ⁻² to 1 × 10 ⁻⁶ mol / min in a solvent such as dimethylformamide or acetonitrile containing a supporting electrolyte such as sodium perchlorate or tetrapropylammonium perchlorate. Approximate the oxidization wave in a straight line by dissolving 1 liter and sweeping to the oxidation side (noble side) using carbon (GC) as the working electrode and rotating platinum electrode as the counter electrode by cyclic voltammetry and DC polarography equipment Then, the intermediate potential of the line segment formed by the intersection of this straight line and the residual current / potential line and the intersection of the straight line and the saturation current line (or the intersection of the straight line parallel to the vertical axis passing through the peak potential value) Values are measured as values for SCE (saturated calomel electrode). This value may deviate by several tens of mil volts due to the influence of the liquid potential difference or the liquid resistance of the sample solution, but the reproducibility of the potential can be ensured by inserting a standard sample (for example, hydroquinone). . The supporting electrolyte and solvent to be used can be selected appropriately depending on the oxidation potential and solubility of the test sample. The supporting electrolytes and solvents that can be used are described in Akira Fujishima et al.

  Specific examples of preferable dyes used in the present invention are shown below, but the dyes used in the present invention are not limited to the following specific examples.

  These (d) colorants are preferably added in an amount of 0.5 to 20% by mass, more preferably 1 to 15% by mass, and 5 to 15% by mass in the ink composition. Is more preferable.

[(E) Sensitizing dye]
The ink composition of the present invention preferably contains (e) a sensitizing dye.
Examples of the (e) sensitizing dye in the present invention include those belonging to the compounds listed below and having an absorption wavelength in a wavelength region of 350 nm to 450 nm.

  For example, polynuclear aromatics (eg, pyrene, perylene, triphenylene, 2-ethyl-9,10-dimethoxyanthracene, etc.), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal, etc.) , Cyanines (eg, thiacarbocyanine, oxacarbocyanine, etc.), merocyanines (eg, merocyanine, carbomerocyani, etc.), thiazines (eg, thionine, methylene blue, toluidine blue, etc.), acridines (eg, Acridine orange, chloroflavin, acriflavine, etc.), anthraquinones (eg, anthraquinone, etc.), squaliums (eg, squalium, etc.), coumarins (eg, 7-diethylamino-4-methylcoumarin, etc.), etc. Mentioned That.

  Preferred examples of the sensitizing dye in the present invention include compounds represented by the following general formulas (vi) to (xi).

In the general formula (vi), A ¹ represents a sulfur atom or NR ^50, R ⁵⁰ represents an alkyl group or an aryl group. L ¹ represents a nonmetallic atomic group that forms a basic nucleus of a dye in cooperation with the adjacent A ¹ and the adjacent carbon atom. R ⁵¹ and R ⁵² each independently represent a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁵¹ and R ⁵² may be bonded to each other to form an acidic nucleus of the dye. W represents an oxygen atom or a sulfur atom.

In general formula (vii), Ar ¹ and Ar ² each independently represent an aryl group and are linked via a bond with L ² . L ² represents —O— or —S—. W is synonymous with that shown in the general formula (vi).

In the general formula (viii), A ² represents a sulfur atom or NR ^59, R ⁵⁹ represents an alkyl group or an aryl group. L ³ represents a nonmetallic atomic group that forms a basic nucleus of a dye in cooperation with adjacent A ² and a carbon atom. R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ and R ⁵⁸ each independently represent a monovalent nonmetallic atomic group.

In general formula (ix), A ³ and A ⁴ each independently represent —S—, —NR ⁶² —, or —NR ⁶³ —, and R ⁶² and R ⁶³ each independently represent a substituted or unsubstituted group. Represents an alkyl group, a substituted or unsubstituted aryl group. L ⁴ and L ⁵ each independently represents a nonmetallic atomic group that forms a basic nucleus of a dye in cooperation with adjacent A ³ , A ⁴ and adjacent carbon atoms. R ⁶⁰ and R ⁶¹ each independently represent a hydrogen atom or a monovalent nonmetallic atomic group. R ⁶⁰ and R ⁶¹ may be bonded to each other to form an aliphatic or aromatic ring.

In general formula (x), R ⁶⁶ represents an aromatic ring or a hetero ring which may have a substituent. A ⁵ represents an oxygen atom, a sulfur atom, or —NR ⁶⁷ —. R ⁶⁴ , R ⁶⁵ and R ⁶⁷ each independently represent a hydrogen atom or a monovalent nonmetallic atomic group. R ⁶⁷ and R ⁶⁴ , and R ⁶⁵ and R ⁶⁷ may be bonded to each other to form an aliphatic or aromatic ring.

In the general formula (xi), R ^{66 to} R ⁷⁵ each independently represent a group composed of a monovalent nonmetallic atomic group.

  Preferable specific examples of the compounds represented by the general formulas (vi) to (xi) include, but are not limited to, those shown below.

These sensitizing dyes may be used alone or in combination of two or more.
The content of (e) the sensitizing dye in the ink composition of the present invention is preferably 0.01 to 20% by mass with respect to the total solid content of the ink composition, from the viewpoint of the colorability of the ink. 15 mass% is more preferable, More preferably, it is the range of 0.5-10 mass%.

[Other ingredients]
Hereinafter, various additives used as necessary for the ink composition of the present invention will be described.

(Co-sensitizer)
To the ink composition of the present invention, a known compound having a function of further improving sensitivity or suppressing polymerization inhibition by oxygen may be added as a co-sensitizer.

  Examples of co-sensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Society”, Vol. 10, 3173 (1972), Japanese Patent Publication No. 44-20189, Japanese Patent Publication No. 51-82102, Japanese Patent Publication No. 52-134692, Japanese Patent Publication No. 59-138205. No. 60-84305, JP-A 62-18537, JP-A 64-33104, Research Disclosure 33825, and the like. Specific examples include triethanolamine. P-dimethylaminobenzoic acid ethyl ester, p-formyldimethylaniline, p-methylthiodimethylaniline and the like.

  Other examples of co-sensitizers include thiols and sulfides such as thiol compounds described in JP-A-53-702, JP-B-55-500806, JP-A-5-142772, No. 56-75643, such as 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercapto. And naphthalene.

Other examples of the co-sensitizer include amino acid compounds (eg, N-phenylglycine), organometallic compounds described in JP-B-48-42965 (eg, tributyltin acetate), JP-B 55- No. 34414, a hydrogen donor described in JP-A-6-308727 (eg, trithiane), a phosphorus compound described in JP-A-6-250387 (eg diethylphosphite), Examples include Si-H and Ge-H compounds described in 191605.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass in terms of solid content.

(Polymerization inhibitor)
A polymerization inhibitor can be added to the ink composition of the present invention from the viewpoint of improving the storage stability. In addition, when the ink composition of the present invention is applied to ink jet recording, it is desirable to heat and reduce the viscosity in the range of 40 to 80 ° C., and thus to prevent head clogging due to thermal polymerization, a polymerization inhibitor Is preferably added.
Examples of such a polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and cuperon Al.
The polymerization inhibitor is preferably added in an amount of 200 to 20000 ppm based on the total amount of the ink composition of the present invention.

[Ultraviolet absorber]
An ultraviolet absorber can be added to the ink composition of the present invention from the viewpoint of improving the weather resistance of the resulting image and preventing discoloration.
Examples of the ultraviolet absorber are described in JP-A-58-185679, JP-A-61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Benzotriazole compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194433, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492 and 56-21141 Cinnamic acid compounds described in JP-A-10-88106, JP-A-4-298503, JP-A-8-53427, JP-A-8-239368, JP-A-10-182621, JP The triazine compounds described in JP-A-8-501291, Research Disclosure No. Examples thereof include compounds described in US Pat. No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds, and so-called fluorescent brighteners.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass in terms of solid content.

〔Antioxidant〕
An antioxidant may be added to the ink composition of the present invention to improve stability. Examples of the antioxidant include European Published Patent No. 223739, No. 309401, No. 309402, No. 310551, No. 310552, No. 4594416, German Published Patent No. 3435443. JP, 54-85535, 62-262417, 63-113536, 63-163351, JP-A-2-262654, JP-A-2-71262, Examples thereof include those described in Kaihei 3-121449, JP-A-5-61166, JP-A-5-119449, US Pat. No. 4,814,262, US Pat. No. 4,980,275, and the like.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass in terms of solid content.

[Anti-fading agent]
In the ink composition of the present invention, various organic and metal complex anti-fading agents can be used. Examples of the organic anti-fading agent include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. Examples of the metal complex anti-fading agent include nickel complexes and zinc complexes. No. 17643, VII, I to J, No. 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in No. 15162 and the compounds included in the general formulas and compound examples of representative compounds described in JP-A-62-215272, pages 127 to 137 can be used. .
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass in terms of solid content.

[Conductive salts]
Conductive salts such as potassium thiocyanate, lithium nitrate, ammonium thiocyanate, and dimethylamine hydrochloride can be added to the ink composition of the present invention for the purpose of controlling ejection properties.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass in terms of solid content.

〔solvent〕
In order to improve the adhesion to the recording medium, it is also effective to add a very small amount of an organic solvent to the ink composition of the present invention.
Examples of the solvent include ketone solvents such as acetone, methyl ethyl ketone, and diethyl ketone, alcohol solvents such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, and tert-butanol, and chlorine such as chloroform and methylene chloride. Solvents, aromatic solvents such as benzene and toluene, ester solvents such as ethyl acetate, butyl acetate and isopropyl acetate, ether solvents such as diethyl ether, tetrahydrofuran and dioxane, glycols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether And ether solvents.
In this case, it is effective to add the solvent within a range that does not cause the problem of solvent resistance and VOC. % Range.

[Polymer compound]
Various polymer compounds can be added to the ink composition of the present invention in order to adjust film physical properties. Examples of polymer compounds include acrylic polymers, polyvinyl butyral resins, polyurethane resins, polyamide resins, polyester resins, epoxy resins, phenol resins, polycarbonate resins, polyvinyl butyral resins, polyvinyl formal resins, shellacs, vinyl resins, acrylic resins. Rubber resins, waxes and other natural resins can be used. Two or more of these may be used in combination. Of these, vinyl copolymer obtained by copolymerization of acrylic monomers is preferred. Furthermore, a copolymer containing “carboxyl group-containing monomer”, “methacrylic acid alkyl ester”, or “acrylic acid alkyl ester” as a structural unit is also preferably used as the copolymer composition of the polymer binder.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass in terms of solid content.

[Surfactant]
A surfactant may be added to the ink composition of the present invention. Examples of the surfactant include those described in JP-A Nos. 62-173463 and 62-183457. For example, anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene blocks Nonionic surfactants such as copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. An organic fluoro compound may be used in place of the surfactant. The organic fluoro compound is preferably hydrophobic. Examples of the organic fluoro compounds include fluorine surfactants, oily fluorine compounds (eg, fluorine oil) and solid fluorine compound resins (eg, tetrafluoroethylene resin). No. (columns 8 to 17) and those described in JP-A Nos. 62-135826.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass in terms of solid content.

In addition to the above, the ink composition of the present invention includes, for example, leveling additives, matting agents, waxes for adjusting film physical properties, and adhesion to recording media such as polyolefin and PET. In order to improve this, a tackifier or the like that does not inhibit the polymerization can be contained.
As the tackifier, specifically, a high molecular weight adhesive polymer described in JP-A-2001-49200, 5-6p (for example, (meth) acrylic acid and an alkyl group having 1 to 20 carbon atoms). An ester with an alcohol having, an ester of (meth) acrylic acid with an alicyclic alcohol having 3 to 14 carbon atoms, a copolymer comprising an ester of (meth) acrylic acid with an aromatic alcohol having 6 to 14 carbon atoms) And a low molecular weight tackifying resin having a polymerizable unsaturated bond.

[Preferred physical properties of ink composition]
When the ink composition of the present invention is applied to inkjet recording, it is preferable that the ink viscosity is 7 to 30 mPa · s, more preferably 7 to 20 mPa · s at the temperature at the time of discharge in consideration of dischargeability. is there. It is preferable that the composition ratio is appropriately adjusted and determined so as to be in the above range. The viscosity of the ink composition at room temperature (25 to 30 ° C.) is 35 to 500 mPa · s, preferably 35 to 200 mPa · s. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be prevented, uncured monomer can be reduced, and odor can be reduced. Dot bleeding at the time of landing can be suppressed, and as a result, the image quality is improved. If the ink viscosity at 25 to 30 ° C. is less than 35 mPa · s, the effect of preventing bleeding is small, and conversely if it is greater than 500 mPa · s, there is a problem in the delivery of the ink liquid.

  The surface tension of the ink composition of the present invention is preferably 20 to 30 mN / m, more preferably 23 to 28 mN / m. When recording on various recording media such as polyolefin, PET, coated paper, and non-coated paper, 20 mN / m or more is preferable from the viewpoint of bleeding and penetration, and the wettability is preferably 30 mN / m or less.

The ink composition of the present invention thus adjusted is suitably used as an ink for inkjet recording. Specifically, the ink composition of the present invention is ejected onto a recording medium by an ink jet printer, and then the ejected ink composition is cured by irradiation with actinic radiation to perform recording.
In the printed matter obtained with this ink, the image portion is cured by irradiation with actinic radiation such as ultraviolet rays, and the strength of the image portion is excellent. Therefore, in addition to image formation with ink, for example, an ink receiving layer ( It can be used for various purposes such as formation of an image portion.

[Inkjet recording method and inkjet recording apparatus]
Next, an ink jet recording method of the present invention and an ink jet recording apparatus to which the recording method can be applied will be described.

The inkjet recording method of the present invention comprises a step of ejecting the ink composition of the present invention described above onto a recording medium by an inkjet printer, and a step of curing the ink composition ejected by irradiation with actinic radiation. It is characterized by including.
In such an ink jet recording method of the present invention, it is preferable that the ink composition is heated to 40 to 80 ° C. to lower the viscosity of the ink composition to 7 to 30 mPa · s and then discharged. High ejection stability can be realized by using.
In general, radiation curable ink compositions generally have a higher viscosity than aqueous inks, so that the viscosity fluctuation range due to temperature fluctuations during printing is large. This viscosity variation of the ink composition directly affects the droplet size and droplet ejection speed as it is, which causes image quality deterioration. Therefore, it is necessary to keep the ink composition temperature as constant as possible during printing. is there. The control range of the ink composition temperature is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and further preferably set temperature ± 1 ° C.

Next, the irradiation conditions of the active radiation in the inkjet recording method of the present invention will be described in detail.
A basic method for irradiating actinic radiation is disclosed in JP-A-60-132767. Specifically, the light source is provided on both sides of the head unit that discharges the ink composition, and the head unit and the light source are scanned by a shuttle method. Irradiation with actinic radiation is performed after a certain period of time after the ink composition has landed on the recording medium.
Further, the curing of the ink composition may be completed by another light source that is not driven. Specifically, in WO99 / 54415, as an irradiation method, a method using an optical fiber or a collimated light source is applied to a mirror surface provided on the side surface of the head unit, and UV light is applied to the recording portion (ink composition application region). A method of irradiating is disclosed. In the present invention, these irradiation methods can be used.

In the ink jet recording method of the present invention, α rays, γ rays, X rays, ultraviolet rays, visible rays, infrared rays, electron beams and the like are used as actinic radiation. The peak wavelength of this actinic radiation is, for example, 200 to 600 nm, preferably 300 to 450 nm, more preferably 350 to 450 nm, although it depends on the absorption characteristics of the sensitizing dye in the ink composition. is there. In addition, since the ink composition of the present invention includes (a) a specific mercapto group-containing polymer and (c) a polymerization initiator, the ink composition has sufficient sensitivity even with low output radiation. Accordingly, the radiation output is, for example, 2,000 mJ / cm ² or less, preferably 10 to 2,000 mJ / cm ² , more preferably 20 to 1,000 mJ / cm ² , and still more preferably 50 to 800 mJ / cm ² . A radiation energy of cm ² is appropriate. The active radiation, exposure surface illuminance (the maximum illuminance of the surface of the recording medium) is, for example, 10 to 2,000 mW / cm ^2, preferably, suitably it is irradiated at 20 to 1,000 mW / cm ² is there.
In particular, in the inkjet recording method of the present invention, the radiation irradiation generates ultraviolet rays having an emission wavelength peak of 360 to 420 nm and a maximum illuminance on the surface of the recording medium of 10 to 1,000 mW / cm ^2. Irradiation from a light emitting diode is preferred.

In the inkjet recording method of the present invention, it is appropriate that the active radiation is applied to the ink composition ejected on the recording medium, for example, for 0.01 to 120 seconds, preferably for 0.1 to 90 seconds. It is.
Furthermore, in the ink jet recording method of the present invention, the ink composition is heated to a constant temperature, and the time from the landing of the ink composition on the recording medium to the irradiation of actinic radiation is 0.01 to 0.5 seconds. Preferably, the time is 0.01 to 0.3 seconds, more preferably 0.01 to 0.15 seconds. Thus, by controlling the time from the landing of the ink composition to the recording medium to the irradiation of the active radiation to an extremely short time, it is possible to prevent the landed ink composition from bleeding before curing. . In addition, since the ink composition can be exposed to a porous recording medium before it penetrates to a deep part where the light source does not reach, residual unreacted monomer can be suppressed, and as a result, odor can be reduced. Can do.

As described above, according to the ink jet recording method of the present invention as described above, by using the ink composition of the present invention, an image is formed with high sensitivity, and ink bleeding and odor are suppressed. Can do. As a result, the dot diameter of the landed ink composition can be kept constant even on various recording media having different surface wettability, and the image quality is improved. In particular, when the viscosity of the ink composition at 25 ° C. is 35 to 500 MP · s, a great effect can be obtained.
For these reasons, the ink composition of the present invention is ejected by an ink jet printer onto a printed matter obtained by the ink jet recording method of the present invention, that is, a recording medium, and then the ink composition is irradiated with actinic radiation. The printed matter obtained by curing (the printed matter of the present invention) has excellent image quality.

  In order to obtain a color image using the ink jet recording method of the present invention, it is preferable to superimpose in order from the color with the lowest brightness. It is preferable to superimpose colors in ascending order of brightness. By superimposing the inks in the order of low lightness, actinic radiation easily reaches the lower ink, and good curing sensitivity, reduction of residual monomers, reduction of odor, and improvement of adhesion can be expected. Moreover, although irradiation with actinic radiation can inject all colors and expose them collectively, exposure for each color is preferred from the viewpoint of promoting curing.

  There is no restriction | limiting in particular as an inkjet recording device used for this invention, A commercially available inkjet recording device can be used. That is, in the present invention, recording can be performed on a recording medium using a commercially available inkjet recording apparatus.

As such an ink jet recording apparatus, for example, an apparatus including an ink supply system, a temperature sensor, and a radiation source is used.
The ink supply system includes, for example, an original tank containing the ink jet recording ink of the present invention, a supply pipe, an ink supply tank immediately before the ink jet head, a filter, and a piezo ink jet head. The piezo-type inkjet head has a multi-size dot of 1 to 100 pl, preferably 8 to 30 pl, for example, 320 × 320 to 4000 × 4000 dpi, preferably 400 × 400 to 2400 × 2400 dpi, more preferably 1200 × 1200 dpi. It can drive so that it can inject with the resolution of. In the present invention, dpi represents the number of dots per 2.54 cm.

  Further, as described above, the radiation curable ink such as the ink composition of the present invention desirably has a constant temperature for the ejected ink composition. It is preferable to perform heating. The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors at each piping site and perform heating control according to the ink flow rate and the environmental temperature. The temperature sensor can be provided near the ink supply tank and the nozzle of the inkjet head. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of thermal energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

  Further, mercury lamps, gas / solid lasers and the like are mainly used as the active radiation source, and mercury lamps and metal halide lamps are widely known as ultraviolet light curable ink jets. However, from the viewpoint of environmental protection, mercury-free is strongly desired, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, LED (UV-LED) and LD (UV-LD) are small, have a long lifetime, high efficiency, and low cost, and are expected as light sources for photo-curable ink jets.

  As described above, a light emitting diode (LED) and a laser diode (LD) can be used as the active radiation source. In particular, when an ultraviolet light source is required, an ultraviolet LED and an ultraviolet LD can be used. For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. Further, when shorter wavelengths are required, US Pat. No. 6,084,250 discloses an LED that can emit radiation centered between 300 nm and 370 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands. Particularly preferred radiation sources in the present invention are UV-LEDs, and particularly preferred are UV-LEDs having a peak wavelength in the range of 350 to 420 nm.

[Recording medium]
The recording medium to which the ink composition of the present invention can be applied is not particularly limited, and various kinds of non-absorbing resin materials used for ordinary non-coated paper, coated paper, so-called soft packaging, or the like. A resin film formed into a film can be used, and examples of the various plastic films include PET film, OPS film, OPP film, ONy film, PVC film, PE film, and TAC film. In addition, examples of the plastic that can be used as a recording medium material include polycarbonate, acrylic resin, ABS, polyacetal, PVA, and rubbers. Metals and glasses can also be used as the recording medium.
In the ink composition of the present invention, when a material with low thermal shrinkage at the time of curing is selected, the adhesive property between the cured ink composition and the recording medium is excellent. Films that tend to curl and deform, such as heat-shrinkable PET film, OPS film, OPP film, ONy film, PVC film, etc., have the advantage that a high-definition image can be formed.

[Lithographic printing plate]
A preferable application example of the ink composition of the present invention is use in a lithographic printing plate.
This lithographic printing plate forms a hydrophobic region by discharging the ink composition of the present invention onto a hydrophilic support using an inkjet recording apparatus or the like and then irradiating the ink composition to cure the ink composition. It becomes. As a result, an image-like hydrophobic ink-receptive region is formed on the surface of the hydrophilic support. When ink and an aqueous component are supplied thereto, the aqueous component is exposed in the hydrophilic support. The ink is held in the hydrophobic region, and the printing process can be performed as it is.

Since the ink composition of the present invention exhibits excellent curability upon irradiation with actinic radiation, the lithographic printing plate of the present invention to which the ink composition is applied has an image portion with excellent printing durability and excellent image quality. become.
Further, by using an ink jet recording method (ink jet recording apparatus) to form an image portion, a high-definition lithographic printing plate image portion can be formed directly from digital data. In addition, regarding the inkjet recording method (inkjet recording apparatus) when producing a lithographic printing plate, each condition and inkjet recording apparatus in the above-described inkjet recording method of the present invention can be applied.
The ink composition of the present invention described above may be applied as it is to the ink composition used for preparing the lithographic printing plate.

[Support]
The support preferably used in preparing the lithographic printing plate of the present invention will be described.
The support used for the lithographic printing plate of the present invention is not particularly limited as long as it is a dimensionally stable plate-like support. If the material constituting the support has surface hydrophilicity, it may be used as it is, or the surface of the plate-like material constituting the support may be subjected to a hydrophilic treatment.
Examples of the material constituting the support include paper, paper laminated with plastic (eg, polyethylene, polypropylene, polystyrene, etc.), metal plate (eg, aluminum, zinc, copper, etc.), and plastic film (eg, diacetic acid). Cellulose, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), paper or plastic film laminated or vapor-deposited with the above metals Etc. A preferable support includes a polyester film and an aluminum plate. Among these, an aluminum plate that has good dimensional stability and is relatively inexpensive is preferable.

  The aluminum plate is a pure aluminum plate, an alloy plate containing aluminum as a main component and containing a trace amount of foreign elements, or a plastic laminated on a thin film of aluminum or aluminum alloy. Examples of foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The content of foreign elements in the alloy is preferably 10% by mass or less. In the present invention, a pure aluminum plate is preferable, but completely pure aluminum is difficult to manufacture in terms of refining technology, and therefore may contain a slightly different element. The composition of the aluminum plate is not specified, and a publicly known material can be used as appropriate.

  The thickness of the support is preferably from 0.1 to 0.6 mm, more preferably from 0.15 to 0.4 mm.

  Prior to using the aluminum plate, it is preferable to perform a surface treatment such as roughening treatment or anodizing treatment. By the surface treatment, it is easy to improve hydrophilicity and secure adhesion between the image recording layer and the support. Prior to roughening the aluminum plate, a degreasing treatment with a surfactant, an organic solvent, an alkaline aqueous solution or the like for removing rolling oil on the surface is performed as desired.

The surface roughening treatment of the aluminum plate is performed by various methods. For example, mechanical surface roughening treatment, electrochemical surface roughening treatment (surface roughening treatment for dissolving the surface electrochemically), chemical treatment, etc. Surface roughening treatment (roughening treatment that chemically selectively dissolves the surface).
As a method for the mechanical surface roughening treatment, a known method such as a ball polishing method, a brush polishing method, a blast polishing method, or a buff polishing method can be used. Also, a transfer method in which the uneven shape is transferred with a roll provided with unevenness in the aluminum rolling step may be used.
Examples of the electrochemical surface roughening treatment include a method in which an alternating current or a direct current is used in an electrolytic solution containing an acid such as hydrochloric acid or nitric acid. Another example is a method using a mixed acid as described in JP-A-54-63902.

  The surface-roughened aluminum plate is subjected to an alkali etching treatment using an aqueous solution of potassium hydroxide, sodium hydroxide or the like, if necessary, further neutralized, and if desired, wear resistant. In order to increase the anodic oxidation treatment.

As an electrolyte used for anodizing treatment of an aluminum plate, various electrolytes that form a porous oxide film can be used. In general, sulfuric acid, hydrochloric acid, oxalic acid, chromic acid or a mixed acid thereof is used. The concentration of these electrolytes is appropriately determined depending on the type of electrolyte.
The conditions for anodizing treatment vary depending on the electrolyte used and cannot be specified in general. In general, however, the electrolyte concentration is 1 to 80% by mass solution, the liquid temperature is 5 to 70 ° C., and the current density is 5 to 60 A / day. dm ² , voltage 1 to 100 V, and electrolysis time 10 seconds to 5 minutes are preferable. The amount of the anodized film formed is preferably from 1.0 to 5.0 g / m ^2, and more preferably 1.5 to 4.0 g / m ^2. Within this range, good printing durability and good scratch resistance of the non-image area of the lithographic printing plate can be obtained.

  As the support used in the present invention, the substrate having the above-mentioned surface treatment and having an anodized film may be used as it is, but for further improvement in adhesion to the upper layer, hydrophilicity, resistance to contamination, heat insulation and the like. If necessary, the surface of the anodized film described in JP-A-2001-253181 and JP-A-2001-322365 may be enlarged or sealed, and the surface may be immersed in an aqueous solution containing a hydrophilic compound. A hydrophilic treatment or the like can be appropriately selected and performed. Of course, these enlargement processing and sealing processing are not limited to those described above, and any conventionally known method can be performed.

[Sealing treatment]
Sealing treatment includes vapor sealing, single treatment with zirconic fluoride, treatment with aqueous solution containing inorganic fluorine compounds such as treatment with sodium fluoride, vapor sealing with addition of lithium chloride, sealing with hot water. Hole processing is also possible.
Among these, a sealing treatment with an aqueous solution containing an inorganic fluorine compound, a sealing treatment with water vapor, and a sealing treatment with hot water are preferable.

[Hydrophilic treatment]
Examples of the hydrophilization treatment used in the present invention include US Pat. Nos. 2,714,066, 3,181,461, 3,280,734, and 3,902,734. There is an alkali metal silicate method as described in the book. In this method, the support is immersed in an aqueous solution such as sodium silicate or electrolytically treated. In addition, the treatment with potassium zirconate fluoride described in JP-B 36-22063, U.S. Pat. Nos. 3,276,868, 4,153,461 and 4,689, And a method of treating with polyvinylphosphonic acid as described in each specification of No.272.

  The support of the present invention preferably has a center line average roughness of 0.10 to 1.2 μm. Within this range, good adhesion to the image recording layer, good printing durability and good stain resistance can be obtained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the embodiments in these examples.

[Synthesis Example 1: Synthesis of specific mercapto group-containing polymer (SP-2)]
4-vinylbenzyloxybenzaldehyde obtained by synthesizing p-chloromethylstyrene (manufactured by Seimi Chemical Co., Ltd.) and p-hydroxybenzaldehyde with potassium carbonate by heating and refluxing in ethanol for 6 hours and recrystallizing from ethanol. 70 g and 30 g of methacrylic acid in 200 g of 1,4-dioxane were dissolved in a 500 ml four-necked round bottom flask equipped with a nitrogen inlet tube, a thermometer, a reflux tube and a stirrer. The internal temperature was kept at 65 ° C., and 1 g of azobisdimethylvaleronitrile (V-65 manufactured by Wako Pure Chemical Industries) was added as an initiator to initiate the polymerization. After continuing heating and stirring for 6 hours, 39 g of 2-amino-5-mercapto-1,3,4-thiadiazole and 100 ml of dimethylformamide were added, and the mixture was heated and stirred at an internal temperature of 85 ° C. for 3 hours. After cooling the reaction system to room temperature, the whole was transferred into 3 L of distilled water, and the deposited precipitate was recovered by decantation and dried. The molecular weight was measured by GPC using THF as an eluent, and the weight average molecular weight was 100,000 in terms of polystyrene. Moreover, the absorption of the proton based on an aldehyde group disappeared by H-nmr measurement, and it was estimated that the structure of the specific mercapto group-containing polymer (SP-2) was obtained.

[Synthesis Example 2: Synthesis of specific mercapto group-containing polymer (SP-5)]
70 g of the monomer (m-1) synthesized from p-chloromethylstyrene and bismuthiol by the method described in Synthesis Example 2 of JP-A-8-184967 and 30 g of methacrylic acid are dissolved in 50 g of potassium hydroxide. Dissolved in 400 g of ethanol, transferred to a 1-liter four-necked round bottom flask equipped with a nitrogen inlet tube, thermometer, reflux tube, and stirrer, kept at an internal temperature of 65 ° C. on a water bath, and azobisdimethyl as an initiator. Polymerization was started by adding 1 g of valeronitrile (V-65 manufactured by Wako Pure Chemical Industries, Ltd.). After continuing the stirring with heating for 6 hours, the reaction system was cooled to room temperature, the whole was transferred into 2 L of distilled water, concentrated hydrochloric acid was gradually added until pH 2 was reached, and the deposited precipitate was collected by decantation and dried. . The molecular weight was measured by GPC using THF as an eluent, and the weight average molecular weight was 130,000 in terms of polystyrene. In addition, the structure of the specific mercapto group-containing polymer (SP-5) was estimated by H-nmr measurement. s

<Preparation of ink composition>
Using each dispersion prepared as described above, each color ink composition was prepared according to the method described below.

(Yellow ink 1: Example 1-1)
(A) a specific specific mercapto group-containing polymer; 5 parts by mass of the (SP-2); (b) a polymerizable compound;
Compound c having the following structure 30 parts by mass Compound d having the following structure 7 parts by mass Hexamethylene diacrylate 40 parts by mass (c) polymerization initiator;
Darocur TPO 7 parts by mass
(The following structure, manufactured by Ciba Specialty Chemicals)
(D) Colorant; C.I. I. Pigment Yellow 13 5 parts by mass; (e) sensitizing dye;
Darocur ITX 3 parts by mass
(The following structure, manufactured by Ciba Specialty Chemicals)
・ Polymerization inhibitor (Cuperon Al: Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Yellow ink 2: Example 1-2)
(A) specific specific mercapto group-containing polymer; (SP-5) 5 parts by mass; (b) polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Stearyl acrylate 40 parts by mass (c) Polymerization initiator;
Irgacure 907 7 parts by mass
(The following structure, manufactured by Ciba Specialty Chemicals)
(D) Colorant; C.I. I. Pigment Yellow 13 5 parts by mass; (e) sensitizing dye;
Darocur ITX 3 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
・ Polymerization inhibitor (Cuperon Al: Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Yellow ink 3: Example 1-3)
-(A) specific specific mercapto group-containing polymer; 5 parts by mass of (SP-11)-(b) polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 40 parts by mass. (C) Polymerization initiator; Compound having the following structure 7 parts by mass. (D) Colorant; I. Pigment Yellow 13 5 parts by mass; (e) sensitizing dye;
Darocur ITX 3 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
・ Polymerization inhibitor (Cuperon Al: Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Yellow ink 4: Comparative example 1)
(A) a comparative mercapto compound;
2-mercaptobenzothiazole 5 parts by mass. (B) polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 40 parts by mass (c) Polymerization initiator;
Irgacure 907 7 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
(D) Colorant; C.I. I. Pigment Yellow 13 5 parts by mass; (e) sensitizing dye;
Darocur ITX 3 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
・ Polymerization inhibitor (Cuperon Al: Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Cyan ink 1: Example 2-1)
(A) a specific specific mercapto group-containing polymer; 5 parts by mass of the (SP-2); (b) a polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 50 parts by mass (c) Polymerization initiator;
Darocur TPO 7 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
(D) Colorant; C.I. I. Pigment Blue 15: 3 5 parts by mass; (e) sensitizing dye;
Darocur ITX 3 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
・ Polymerization inhibitor (Cuperon Al: Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Cyan ink 2: Example 2-2)
(A) specific specific mercapto group-containing polymer; (SP-5) 5 parts by mass; (b) polymerizable compound;
Compound c of the above structure 30 parts by mass Compound d of the above structure 7 parts by mass Hexamethylene diacrylate 50 parts by mass (c) polymerization initiator; LD-5 (the following structure) 5 parts by mass (d) Colorant;
Dye d-42 (oxidation potential 1.28 V (vs SCE)) 5 parts by mass (e) sensitizing dye;
7-diethylamino-4-methylcoumarin (the following structure) 3 parts by mass / polymerization inhibitor (Cuperon Al: manufactured by Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Cyan ink 3: Example 2-3)
-(A) specific specific mercapto group-containing polymer; 5 parts by mass of (SP-11)-(b) polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 50 parts by mass. (C) Polymerization initiator; LD-5 (the above structure) 5 parts by mass. (D) Colorant;
The dye d-51 (oxidation potential 0.83 V (vs SCE)) 5 parts by mass; (e) sensitizing dye;
7-diethylamino-4-methylcoumarin (the above structure) 3 parts by mass / polymerization inhibitor (Cuperon Al: manufactured by Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Cyan ink 4: Comparative example 2)
(A) a comparative mercapto compound;
2-mercaptobenzimidazole 5 parts by mass. (B) polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 50 parts by mass. (C) Polymerization initiator; LD-5 (the above structure) 5 parts by mass. (D) Colorant; I. Pigment Blue 15: 3 5 parts by mass; (e) sensitizing dye;
7-diethylamino-4-methylcoumarin (the above structure) 3 parts by mass / polymerization inhibitor (Cuperon Al: manufactured by Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Magenta ink 1: Example 3-1)
(A) a specific specific mercapto group-containing polymer; 5 parts by mass of the (SP-2); (b) a polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 50 parts by mass. (C) Polymerization initiator; LD-5 (the above structure) 5 parts by mass. (D) Colorant; I. Pigment Red 57: 1 5 parts by mass. (E) Sensitizing dye;
7-diethylamino-4-methylcoumarin (the above structure) 3 parts by mass / polymerization inhibitor (Cuperon Al: manufactured by Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Magenta ink 2: Example 3-2)
(A) specific specific mercapto group-containing polymer; (SP-5) 5 parts by mass; (b) polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 50 parts by mass. (C) Polymerization initiator; LD-5 (the above structure) 5 parts by mass. (D) Colorant; I. Pigment Red 57: 1 5 parts by mass. (E) Sensitizing dye;
2-ethyl-9,10-dimethoxyanthracene (the following structure) 3 parts by mass / polymerization inhibitor (Cuperon Al: manufactured by Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Magenta ink 3: Example 3-3)
-(A) specific specific mercapto group-containing polymer; 5 parts by mass of (SP-11)-(b) polymerizable compound;
Compound a having the following structure: 40 parts by mass Compound b having the following structure: 40 parts by mass. (C) Polymerization initiator;
Irgacure 250 7 parts by mass
(The following structure, manufactured by Ciba Specialty Chemicals)
(D) Colorant; C.I. I. Pigment Red 57: 1 5 parts by mass. (E) Sensitizing dye;
Darocur ITX 3 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
-Polymerization inhibitor (ethanolamine) 5 parts by mass

(Magenta ink 4: Example 3-4)
(A) specific specific mercapto group-containing polymer; (SP-12) 5 parts by mass; (b) polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 50 parts by mass (c) Polymerization initiator;
Darocur TPO 7 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
(D) Colorant; C.I. I. Pigment Red 57: 1 5 parts by mass. (E) Sensitizing dye;
Darocur ITX 3 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
・ Polymerization inhibitor (Cuperon Al: Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Magenta ink 5: Comparative example 3)
(A) a comparative mercapto compound;
2-mercaptobenzothiazole 5 parts by mass. (B) polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 50 parts by mass. (C) Polymerization initiator; LD-5 (the above structure) 5 parts by mass. (D) Colorant; I. Pigment Red 57: 1 5 parts by mass. (E) Sensitizing dye;
7-diethylamino-4-methylcoumarin (the above structure) 3 parts by mass / polymerization inhibitor (Cuperon Al: manufactured by Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Magenta ink 6: Comparative example 4)
(B) a polymerizable compound;
45 parts by weight of the compound a having the above structure 40 parts by weight of the compound b having the above structure (c) a polymerization initiator;
Irgacure 250 7 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
(D) Colorant; C.I. I. Pigment Red 57: 1 5 parts by mass. (E) Sensitizing dye;
Darocur ITX 3 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
-Polymerization inhibitor (ethanolamine) 5 parts by mass

(Black ink 1: Example 4-1)
(A) a specific specific mercapto group-containing polymer; 5 parts by mass of the (SP-2); (b) a polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 50 parts by mass (c) Polymerization initiator;
Darocur TPO 7 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
(D) Colorant; C.I. I. Pigment Black 7 5 parts by mass; (e) sensitizing dye;
Darocur ITX 3 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
・ Polymerization inhibitor (Cuperon Al: Wako Pure Chemical Industries, Ltd.) 3 parts by mass

(Black ink 2: Example 4-2)
(A) specific specific mercapto group-containing polymer; (SP-5) 5 parts by mass; (b) polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 50 parts by mass (c) Polymerization initiator;
Irgacure 250 7 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
(D) Colorant; C.I. I. Pigment Black 7 5 parts by mass; (e) sensitizing dye;
Darocur ITX 3 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
-Polymerization inhibitor (Cuperon Al: Wako Pure Chemical Industries, Ltd.) 5 parts by mass

(Black ink 3: Comparative example 5)
(B) a polymerizable compound;
Compound c having the above structure 30 parts by mass Compound d having the above structure 7 parts by mass Hexamethylene diacrylate 55 parts by mass. (C) Polymerization initiator;
Darocur TPO 7 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
(D) Colorant; C.I. I. Pigment Black 7 5 parts by mass; (e) sensitizing dye;
Darocur ITX 3 parts by mass
(The above structure, manufactured by Ciba Specialty Chemicals)
・ Polymerization inhibitor (Cuperon Al: Wako Pure Chemical Industries, Ltd.) 3 parts by mass

The crude composition of each color prepared as described above was filtered with a filter having an absolute filtration accuracy of 2 μm to obtain an ink composition of each color.
In the ink compositions of the above examples and comparative examples, the ink viscosity at the ink discharge temperature is 7 to 20 mPa.s. It was within the range of s.

[Inkjet image recording]
Image printing was performed using the ink compositions of Examples and Comparative Examples prepared as described above.
Image printing was performed by recording on a support (recording medium) using a commercially available inkjet recording apparatus having a piezoelectric inkjet nozzle.
As the support (recording medium) used, a grained aluminum support, a surface-treated transparent biaxially oriented polypropylene film with printability, a soft vinyl chloride sheet, cast coated paper, and commercially available recycled paper were used. used.
The ink supply system of the ink jet recording apparatus includes an original tank, a supply pipe, an ink supply tank immediately before the ink jet head, a filter, and a piezo ink jet head, and heat insulation and heating are performed from the ink supply tank to the ink jet head portion. Temperature sensors were provided near the ink supply tank and the nozzles of the ink jet head, respectively, and temperature control was performed so that the nozzle portions were always 70 ° C. ± 2 ° C. The piezo-type inkjet head was driven so that multi-size dots of 8 to 30 pl could be ejected with a resolution of 720 × 720 dpi. After landing, UV-LED light with a peak wavelength of 395 nm is condensed to an exposure surface illuminance of 100 mW / cm ² , and the exposure system, main scanning speed, and emission are set so that irradiation starts 0.1 seconds after ink landing on the recording medium. The frequency was adjusted. Further, the exposure time was variable, and exposure energy was irradiated. In the present invention, dpi represents the number of dots per 2.54 cm.
Using each ink of the example and the comparative example, the ink was ejected at an environmental temperature of 25 ° C. and irradiated with the UV-LED light.

<Evaluation of inkjet image>
For each formed image, in accordance with the method described below, the sensitivity required for curing, ink bleeding on a grained aluminum support, adhesion, printing durability, and storage stability were evaluated. went.

(Measurement of curing sensitivity)
The amount of exposure energy (mJ / cm ² ) at which the sticky feeling disappears on the image surface after ultraviolet irradiation was defined as the curing sensitivity. The smaller the value, the higher the sensitivity.

(Evaluation of ink bleeding on grained aluminum support)
For images printed on a grained aluminum support, ink bleeding was evaluated according to the following criteria.
○: No blur between adjacent dots Δ: Slightly blur dots ×: Dot blurs and the image is clearly blurred

(Evaluation of adhesion in grained aluminum support)
With respect to the print image created above, a sample that does not scratch the print surface at all, and in accordance with JISK 5400, 11 cuts are made on the print surface at 1 mm intervals vertically and horizontally, and a 1 mm square grid 100 is formed. Samples made individually are prepared, cellotape (registered trademark) is pasted on each printing surface, peeled off quickly at an angle of 90 degrees, and the remaining printed images or grids are evaluated according to the following criteria. did.
○: No peeling of the printed image is observed even in the cross cut test. Δ: Some peeling of the ink is recognized in the cross cut test, but almost no peeling is observed unless the ink surface is scratched. Easy to peel off with cello tape (registered trademark)

(Evaluation of printing durability)
The image printed on the grained aluminum support prepared above was used as a printing plate, and after printing with a Heidel KOR-D machine, a relative comparison was made using the number of printed sheets as an index of printing durability (Example 1-1 was 100). ) A larger numerical value is preferable because it has a higher printing durability.

(Evaluation of storage stability)
After the ink compositions prepared in Examples and Comparative Examples were stored at 75% RH and 60 ° C. for 3 days, the ink viscosity at the ejection temperature was measured, and the increase in ink viscosity was determined as the viscosity after storage / before storage. Expressed as a ratio. It was judged that the storage stability was good when the viscosity did not change and was close to 1.0, and when it was less than 1.5, the storage stability was determined.
These evaluation results are shown in Table 1 below.

  From Table 1, all of the ink compositions of Examples 1-1 to 4-2 (ink composition of the present invention) are highly sensitive to irradiation with actinic radiation, and also have good storage stability. I know that there is. In addition, when this ink composition is used for image formation on an aluminum support, it can form a high-quality image without ink bleeding of the dots, and the image has good adhesion to the support. Can also be seen as excellent. Furthermore, it can be seen that even when the ink composition of the present invention is used for preparing a printing plate, excellent printing durability is exhibited.

  In addition, the ink bleeding evaluation and adhesion evaluation described above were conducted by replacing the aluminum support with a surface-treated transparent biaxially stretched polypropylene film, soft vinyl chloride sheet, cast coated paper, and commercially available recycled paper. When each paper was used, it was found that the same results as in Table 1 were obtained.

Claims (10)

  An ink composition comprising: (a) a polymer having a heterocyclic group bonded to a mercapto group in its side chain; (b) a polymerizable compound; and (c) a polymerization initiator.   The ink composition according to claim 1, further comprising (d) a colorant.   The ink composition according to claim 2, wherein the colorant (d) is a pigment or an oil-soluble dye.   The ink composition according to claim 3, wherein an oxidation potential of the oil-soluble dye is 1.0 V (vs SCE) or more.   The ink composition according to any one of claims 1 to 4, which is for inkjet recording.   A step of discharging the ink composition according to any one of claims 1 to 5 onto a recording medium by an ink jet printer, and a step of curing the ink composition discharged by irradiating actinic radiation. An ink jet recording method comprising: The actinic radiation is emitted from a light emitting diode that emits ultraviolet rays having an emission wavelength peak of 360 to 420 nm and a maximum illuminance on the surface of the recording medium of 10 to 1,000 mW / cm ^2. The inkjet recording method according to claim 6.   A printed matter obtained by ejecting the ink composition according to any one of claims 1 to 5 on an ink-jet printer on a recording medium and then irradiating with active radiation to cure the ink composition.   A hydrophobic region is formed by discharging the ink composition according to any one of claims 1 to 5 onto a hydrophilic support and then irradiating the ink composition to cure the ink composition. A method for producing a lithographic printing plate characterized by the above.   A hydrophobic region formed by ejecting the ink composition according to any one of claims 1 to 5 on a hydrophilic support and then irradiating the ink composition to cure the ink composition. A lithographic printing plate with.